Many portable hand tools are powered by electric motors. They are subjected to heavy use under arduous conditions. Such tools require periodic maintenance including replacement of the commutator brushes. It has, therefore, been important that the brush units of the brush assembly should be easily accessible to enable brush replacement to be carried out quickly and without the use of special tools.
In such tools it is common to provide access to the brush units via access ports in the housings for electric motors, each brush unit having its own access port. However, such an arrangement requires one access hole per brush unit. In addition, the design of the brush units themselves is pre-determined to some extent so that they may be able to be entered and withdrawn through the comparatively small access ports. Recently, it is also common practice to employ thermoplastic materials for the housings despite the fact that such materials deteriorate in the presence of heat and it is found that deterioration is most likely to occur in those parts of the housing in the immediate vicinity of the commutator brushes.